(1) Field of the Invention
The present invention relates to the improvement of the yield and vigor of agronomic plants, and more particularly to a method of improving the yield and vigor of agronomic plants by treatment of the plant or its propagation material with certain active agents.
(2) Description of the Related Art
Plants, and in particular, legumes, are a critical source of food, animal feed, fiber, and useful chemicals and medicaments. The ability of legumes to fix nitrogen provides this order of plants with the unusual ability to provide high quality nutritional proteins as well as to improve the nitrogen content of the soils in which they grow. One species of legume—the soybean—is an ancient and important worldwide crop. Relatively easy to grow and subject to relatively few important insect pests, compared with other important agronomic crops, soybeans provide oil and high protein meal for human and animal consumption and for industrial uses.
In the United States, about 70 million acres are planted to soybeans each year and recent annual soybean production has been over 2.5 billion bushels. The average yield of soybeans in the United States has been steadily increasing over the past 75 years from an initial level of about 11 bu/ac, to the present level of about 35 to 40 bu/ac. (See, United States Department of Agriculture, National Agricultural Statistics Service, Crop Report, June 2000, Washington, D.C.). Better strains of seed and the systematic improvement of agricultural and pest management practices have facilitated this improvement.
Where the growing season permits in the Midwestern United States, soybeans are typically grown in rotation with field corn and sometimes in a double-crop after winter wheat is harvested. Conservation tillage practices are regularly used for soybeans and from one-fourth to about one-third of the acreage is no-tilled. About two-thirds of all soybeans are solid seeded (sown in narrow, 6″, 7″, or 8″ rows). The benefits of solid seeding a soybean crop are that the canopy closes quickly and can reduce weed growth and, hence the need for late season post emergence herbicides. This eliminates the possibility of row cultivation and late season application of pesticides by ground application.
In the U.S. Midwest, soybeans are rarely treated for insect pests, and the few insects that can cause crop loss include bean leaf beetle (Cerotoma trifurcata), grasshoppers (Melanoplus spp.), green cloverworm (Plathypena scabra), and potato leafhopper (Empoasca fabae).
Soybean yield can be adversely affected by several diseases, and among these are pythium damping off (Pythium spp.), phytophthera damping off (Phytophthera spp.), rhizoctonia root rot (Rhizoctonia solani), anthracnose (Colletotrichum spp.), stem canker (Diaporthe phaseolorum), septoria leaf spot (Septoria glycines), purple seed stain (Cercospora kikuchii), sudden death syndrome (Fusarium solani), white mold (Sclerotinia sclerotinorum), and brown stem rot (Phialophora gregata). It is known, however, that non-pesticidal management measures are equal to or better than pesticides for the control of many common pathogens. Plant disease management for soybeans has always relied more on agronomic practices than on pesticides, and seed treatment and foliar fungicides, along with nematicides, play a limited role. (See, e.g., information dealing with soybeans on U.S. Department of Agriculture website: http://pestdata.ncsu.edu/cropprofiles/, dated Nov. 4, 2000).
Diseases such as “Take-all disease”, caused by the organism Gaeumannomyces graminis, which are prevalent in cereal crops, have not been reported to affect soybeans.
Seed treatment with fungicides, such as metalaxyl, carboxin, captan and thiram, which are active against the known soybean disease-causing organisms listed above, is common for soybeans, and the impact of fungicidal seed treatment on yield due to the avoidance of stand losses due to these diseases is significant. However, the cost of such seed treatment is modest relative to overall production costs. Moreover, since several fungicides are approved for use on soybeans, if one or two of the fungicides were to be withdrawn, it is likely that one or more other known compounds would be adequate substitutes. Therefore, the incentive to search for different fungicides to act as fungicidal seed treatment compounds for soybeans has been slight.
However, with the limited amount of high quality arable land that is available for row crop production in regions having suitable climate, any method that would improve the vigor and yield of agronomic plants in general, and in particular, for legumes, such as soybeans, would provide a significant advantage. It would be particularly useful if such method was easy to apply.